With the continuous development of ultra-large integration (ULI), the critical dimension (CD) of semiconductor devices has become smaller and smaller. Further, the functionalities of the semiconductor devices have also become broader and broader. The integration level of integrate circuits (ICs) has been developed into a scale where hundreds of millions, or a few billions of devices are integrated in one chip. At the same time, multilayer interconnect techniques utilizing more than two layers of metal interconnect structures have been widely used.
The conventional interconnect structures are usually made of aluminum. With the continuous dimension-reduction of the semiconductor devices, although the size of interconnect structures is continuously reduced, the electric current passing through the interconnect structures has become larger and larger. Further, the responding time of the interconnect structures are required to be shorter and shorter. Thus, the conventional aluminum interconnect structures are unable to match the desired requirements. Therefore, copper has gradually substituted aluminum in the interconnect structures.
Comparing with aluminum, copper has a lower resistivity, and a better anti-electromigration performance. Thus, copper interconnect structures are able to lower the resistance-capacitance (RC) delay of the interconnect structures; improve the anti-electromigration ability; and enhance the reliability of the ICs. Therefore, substituting the aluminum interconnect structures with the copper interconnect structures has become a trend for developmental of the interconnect technology of ICs.
However, although using Cu as a material of interconnect structure is able to improve the performance of interconnect structure, the performance of the interconnect structure needs further improvement, especially when the node dimension further shrinks. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.